cover: Update /get-started/books:

- Remove `.content` from templates.
- Remove a stray unclosed label.

bookwyrm/templates/get_started/book_preview.html

@@ -1,8 +1,8 @@
 {% load i18n %}
-<div class="column is-narrow is-clipped has-text-centered">
-    {% include 'snippets/book_cover.html' with book=book %}
-    <label class="label" for="id_shelve_{{ book.id }}">
-    <div class="select is-small">
+<div class="column is-cover">
+    {% include 'snippets/book_cover.html' with book=book cover_class='is-h-l is-h-m-mobile' %}
+
+    <div class="select is-small mt-1 mb-3">
         <select name="{{ book.id }}" aria-label="{% blocktrans with book_title=book.title %}Have you read {{ book_title }}?{% endblocktrans %}">
             <option disabled selected value>Add to your books</option>
             {% for shelf in request.user.shelf_set.all %}